1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device including a step of grinding a rear surface of a semiconductor wafer.
2. Description of the Related Art
A semiconductor device is manufactured such that a plurality of semiconductor chips each including a semiconductor element is formed on a front surface of a semiconductor wafer. Further, among the semiconductor chips being adjacent to each other on the semiconductor wafer, there are formed scribe lines along which the semiconductor wafer is cut into semiconductor chips in a dicing process. The semiconductor wafer has a thickness of about 500 to 900 μm to maintain certain rigidness in the manufacturing process. However, in a case where the semiconductor wafer is incorporated into a package as a chip, the semiconductor chip is required to have the thickness between 100 to 350 μm. For this reason, adopted is a method in which the semiconductor wafer is ground to obtain a desired thickness, and then the semiconductor wafer is cut vertically and horizontally along the scribe lines to separate.
As a method of thinning a semiconductor wafer, JP 05-335411 A discloses a method of manufacturing a semiconductor chip in which trenches each having a predetermined depth are formed on the front surface side of the semiconductor wafer, and then the rear surface side of the semiconductor wafer is ground.
Further, JP 2001-127029 A discloses a method of protecting the front surface of a semiconductor wafer with a surface protective sheet which includes a base material and an adhesive layer formed thereon, and has a stress relaxation rate of 40% or more in a minute to the tension of 10% in a tension test for surface protective sheet.
In a process of grinding the rear surface of the semiconductor wafer, surface protective tape is bonded to the front surface of the semiconductor wafer so as to protect the front surface of the semiconductor wafer, and then the rear surface of the semiconductor wafer is ground. After the rear surface of the semiconductor wafer is ground, the surface protective tape is removed.
In a case of using a polyimide resin film, the polyimide resin film must have a certain thickness to protect the semiconductor chip from damage or contamination. Besides removal of the polyimide resin film disposed on the scribe lines is necessary since the polyimide resin film disposed on the scribe lines deteriorates cutting performance of a dicing blade in dicing process.
The polyimide resin film is required to have a thickness of 4 μm or more, and each scribe line has a shape of a trench. As shown in FIG. 7, scribe lines 3 are formed in an outer-most circumferential portion of a semiconductor wafer 1. As shown in FIG. 6, a surface protective tape 6 does not fill each trench made by the scribe lines 3 on the front surface of the semiconductor wafer, which results in generating gaps 9 between the surface protective tape and each of the scribe lines formed on the front surface of the semiconductor wafer. As a result, when the rear surface of the semiconductor wafer is ground, grinding water enters from the gaps 9, and grinding swarf contaminates the scribe lines and the front surface of the semiconductor chip.